Polymethyl methacrylate (PMMA) is one of the polymerizates of methyl methacrylate. Polymerizates of methyl methacrylate are light and have high strength and excellent processability and durability, and thus are used widely in various industrial fields, including automobiles, wind screens for airplanes, optical products, displays, lighting instruments, cosmetics, pharmaceuticals, buildings, electric/electronic products, ornaments and general goods. In the cosmetic field, PMMA having a matte feel of use and high oil absorption is used widely for the production of fundamental cosmetics and make-up cosmetics. Particularly, powder including PMMA has high adsorbability to sebum, and thus is used widely for the production of fundamental cosmetics for controlling sebum and make-up cosmetics for modifying a skin color tone. However, since such powder mostly has a highly dense internal structure, there is a limitation in oil absorption. Therefore, a porous structure is required to improve oil absorption. For this, many attempts have been made to develop a porous type of powder. However, most porous powder materials used in the cosmetic field still have a highly dense internal structure and include fine pores with a size of several nanometers merely on the surface thereof. As a result, it is unsure whether such materials actually improve oil absorption or not.
The methods for preparing porous particles according to the related art include allowing a crosslinkable monomer and initiator to be absorbed and polymerized in polymer seed particles, or adding a mixture containing crosslinkable monomers to polymer microparticles and heating the resultant mixture in the presence of an oil-soluble initiator to the decomposition temperature of initiator to carry out polymerization.
Particularly, Korean Patent Laid-Open No. 10-2006-0036614 discloses a method for preparing porous polymethyl methacrylate. In the method, acrylic monomers and multifunctional monomers are polymerized by using a cosolvent formed of an organic solvent and an initiator, and then the cosolvent is removed from the resultant particles while forming nano-sized pores. In general, PMMA powder has an oil absorption of about 0.6 cc per gram. However, it is reported that the thus obtained porous PMMA powder having nano-sized pores has an oil absorption of about 1.8 cc/g to about 2.34 cc/g. In the method, as a cosolvent, an organic solvent such as toluene, n-hexanone, methyl isobutyl ketone or isoamyl alcohol is used. Thus, several times of washing are required undesirably in order to remove such an organic solvent.
In addition, the patent issued to Soken Chemical & Engineering Co., Ltd. (Japanese Patent Publication No. 2005-00055959, U.S. Pat. No. 7,741,378 and Korean Patent Laid-Open No. 10-2007-0115913) discloses porous monodispersed particles and method for production thereof. In the method, particles of polymethyl methacrylate or acrylic resin containing 70 wt % or more of methyl methacrylate as a copolymerizable component are used as seed particles, which, in turn, are swelled with a swelling solution containing at least 70 wt % of methyl methacrylate and 3-8 wt % of divinyl benzene and an oil-soluble polymerization initiator at a weight ratio of 20-80 times of the seed particles. After the swelling, polymerization is carried out to obtain porous particles. However, when preparing porous particles by using monomers and an initiator as mentioned above, the residue may have a negative effect. Thus, the above-mentioned manner of preparation of porous particles for use as a material for pharmaceuticals or cosmetics used directly in the human body not for industrial applications is always risky.
Under these circumstances, the present inventors have conducted many studies to overcome the above-mentioned problems occurring in the related art. As a result, we have found that porous polymethyl methacrylate obtained from a method for preparing macroporous polymethyl methacrylate (PMMA) by using a polymethyl methacrylate (PMMA) polymer and Pluronic polymer has high oil absorption and adsorbability to sebum, and thus it is effective for oil control when used for a fundamental cosmetic and make-up cosmetic composition, and has a low content of residual solvent and impurities, and shows a good feel of use and safety when applied to the skin.